This invention relates to structural building panels made of welded wire having an insulating foam core. This invention also relates to the method for making the welded wire panel and introducing the foam core thereinto.
The utility of foam-core welded wire structural buildings panels in building construction is well established. See, e.g., U.S. Pat. No. 3,305,991 to Weismann. In the past, such panels have been made of planar trusses having top and bottom runner wires that have been arranged into panels by connecting the top runner wires of each truss together with a plurality of transverse wires and connecting the bottom runner wires together in the same manner.
A layer of polyurethane foam has been placed in the prior art panels by supporting the welded wire matrix on a planar surface, introducing a layer of sand into the matrix through the lattice, and applying a layer of liquid polyurethane resin, together with a blowing agent, on the layer of sand. By controlling the depth of the sand and the depth of he foam, a panel can be produced having a layer of foam in the interior spaced from both the front side and the back side of the panel. This method is explained in U.S. Pat. No. 3,555,131 to Weismann, which is hereby incorporated by reference.
Structures are formed from these panels by connecting the panels together in the shape of the desired structure and coating the panels with a layer of material, such as concrete or plaster.
One of the drawbacks of the prior art panels is that, by their very nature, they must be fabricated with a relatively complex welding apparatus. Because of the geometry of those panels, the cross wires can be welded to the struts only by complex electrode movement. The electrodes must not only move up and down into and out of contact with the matrix wires, they must also move sideways in and out of the matrix. The time required for this electrode movement is a severe limiting factor on production speed. In addition, the welding machines ar necessarily complex and expensive. A typical prior art welding machine is shown in U.S. Pat. No. 3,838,241 to Weismann.
Another disadvantage of prior art processes for making foam core structural building panels is the cost of the foam. For example, the process of U.S. Pat. No. 3,555,131 typically uses over two pounds of polyurethane resin per cubic foot of foam in completed product. Polyurethane resin is relatively expensive, and typically accounts for about 50% of the material cost of the panel.
Finally, because of their construction, the prior art panels do not fully utilize the theoretical structural strength of the wire material.
Accordingly, it is an object of the present invention to provide a simplified method for constructing foam-core building panels.
Another object of the present invention is to provide a welded wire panel that fully utilizes the strength of the wire in a fully trussed configuration.
Still another object of the present invention is to provide an improved foam-core panel having superior moisture barrier and insulating properties while using less polyurethane resin.